Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$60.46	4.473%	$63.1644	$63.16	$63.15	$63.20
Purchase #2	$71.87	10.358%	$79.3143	$79.31	$79.30	$79.30
Purchase #3	$71.68	9.246%	$78.3075	$78.31	$78.30	$78.30
Purchase #4	$206.41	12.111%	$231.4083	$231.41	$231.40	$231.40
Purchase #5	$168.78	5.639%	$178.2975	$178.30	$178.30	$178.30
Purchase #6	$63.99	5.304%	$67.384	$67.38	$67.40	$67.40
Purchase #7	$223.55	9.171%	$244.0518	$244.05	$244.05	$244.10
7 purchase totals =	$866.74		$941.9278	$941.92	$941.90	$942.00